Chimpanzee hand preference for throwing and infant cradling: implications for the origin of human handedness

Calvin (i983) has hypothesized that the neurophysiological, perceptual, and cognitive demands of throwing may have served as important evolutionary precursors to a variety of traits( e.g., handedness, tool use, and language processing) in early hominids. Eighty-eight percent of humans throw with their right hands (Healey, Liederman, and Geschwind I986), and Calvin has argued that this right-handed throwing evolved as a result of a left-hemisphere specialization for planned sequential movements. He has further suggested that right-handed throwing would have been more prevalent in females than in males because females predominantly carried infants on the left arm, leaving the right hand available for other actions. Infant carrying has also been hypothesized as a major selective feature in the evolution of bipedalism in hominids (Leakey I976).